In the field of physical medicine and rehabilitation, various professionals are often called upon to assess the functional capacity of a patient. Functional Capacity Evaluations (“FCEs”) are used extensively throughout the United States to ascertain an individual's status in regards to the extent of a disability and/or the ability to return to work. FCEs have assumed particular importance in light of the high cost of worker's compensation claims for industrial accidents.
The ability to lift is one of the critical factors affecting a patient's ability to return to work. Thus one of the most important functions of an FCE is determining the patient's ability to lift particular amounts of weight in particular configurations, including floor to shoulder, floor to waist, knuckle to shoulder, and shoulder to overhead. The question with such tests, however, is always whether the patient has given maximal effort, so that the results of the test present a true picture of the patient's functional capabilities.
At present, there is no system which can accurately determine whether a patient has given maximal effort. While indicators such as mechanical breakdown, postural breakdown, recruitment of accessory muscles, and heart rate may be used, the application of these indicators is to some degree subjective and thus subject to question. Furthermore, many evaluators administering FCE's may have inadequate experience to determine whether true maximal effort was given.
While patients have been known to manipulate FCE results by conscious and unconscious efforts, there are certain variables that cannot be manipulated. In particular, as maximal effort and maximal weights are achieved, the expected outcome is slower time to complete the lift, along with decreased velocity and acceleration.
The most widely given reason for inability to lift additional weight is pain. Pain has been shown to result in decreased range and velocity of motion for affected body segments. It is also well known that when pain is present it affects the strength of muscular contraction. Therefore, if pain is truly present in a given lift, the variables of speed, velocity, and acceleration will be adversely affected. Test results which are inconsistent with these expectations (for example where velocity and acceleration does not decrease significantly between a previous lift and a lift with greater weight claimed to represent “maximal effort,” or where the velocity and acceleration for two lifts of the same weight during different portions of an FCE vary dramatically) may indicate that the patient is not expending maximal effort, or is otherwise attempting to manipulate the test results.
The force distribution between the patient's legs when performing lifts is another objective factor which can be taken into account in assessing functional capacity, particularly for patients who claim either lower back or lower extremity pathology. Many patients with spinal disc pathology have symptoms related to one of the lower extremities, which may impair strength and sensation as well as functional status (e.g. the ability to squat, kneel, climb stairs, lift, etc.). Patients manipulating the system may consciously walk with an antalgic gait and shift their weight more to one side when standing, but during a lift will often unconsciously apply force symmetrically on both legs, thereby illustrating their actual functional status with respect to the allegedly “weak” leg. Measuring force distribution during lifting may also give a physician or rehabilitation professional valuable information regarding the patient's diagnosis and progress during a rehabilitation program.
Likewise, the force distribution between the patient's hands during a lift may shed light on the true condition of patients complaining of pain or weakness in one arm due to upper back pathology or other causes. Further information regarding the relative strength of each arm may also be gathered by utilizing a program of one-armed lifts and collecting information on the velocity, acceleration, and force generated.
Several devices have previously been developed to measure these and other objective indicators during FCEs. For example, Marmer's “Functional capacity assessment system and method”, U.S. Pat. No. 6,056,671, uses digitized video to determine the velocity and acceleration of lifts during a functional capacity evaluation. However, this system makes use of multiple video cameras and a computer system, as well as visual indicators which have to be applied to the patient. Accordingly, the system may be somewhat complex and expensive, and requires substantial time to set up and operate, rendering it unsatisfactory for some FCE applications. Additionally, it provides no mechanism for measuring force distributions between the patient's hands and feet.
Lepley's “Exercise platform for physiological testing,” U.S. Pat. No. 5,271,416, also can be used to collect lift velocity and acceleration information, as well as data regarding the force applied by the patient's feet (though not hands) during a lift. However, this system uses a cable spool with a handle to simulate the lifting of an object, and so may not accurately reproduce the circumstances encountered in a “real world” lift, which is a primary goal in the development of FCE test protocols.
Accordingly, it would be advantageous to have a system for use in FCE testing which could accurately collect velocity, acceleration, and force distribution data in a test format which is already familiar to FCE evaluators and closely mimics actual dynamic lifting conditions, while being relatively inexpensive to manufacture, and easy to set up and operate.